VisualPinball.NativeInput 0.0.2

VPE Native Input Polling

High-performance native input polling library for Visual Pinball Engine.

Purpose

Provides OS-level input polling to achieve sub-millisecond input latency by bypassing Unity's Input System buffer. The input polling runs on a dedicated thread at 500-2000 Hz and forwards events to the simulation thread via a callback.

Architecture

┌─────────────────────────────────────┐
│   OS Input Events (Keyboard/HID)    │
└─────────────────────────────────────┘
              ↓
┌─────────────────────────────────────┐
│  Native Input Polling Thread        │
│  (500-2000 Hz)                      │
├─────────────────────────────────────┤
│  • GetAsyncKeyState (Windows)       │
│  • X11 key polling (Linux)          │
│  • CoreGraphics/AppKit (macOS)      │
└─────────────────────────────────────┘
              ↓
┌─────────────────────────────────────┐
│  Lock-Free SPSC Ring Buffer         │
└─────────────────────────────────────┘
              ↓
┌─────────────────────────────────────┐
│  Simulation Thread (1000 Hz)        │
└─────────────────────────────────────┘

Building

Windows (Visual Studio 2022)

cd VisualPinball.NativeInput
mkdir build
cd build
cmake .. -G "Visual Studio 17 2022" -A x64
cmake --build . --config Release

Output: ../VisualPinball.Engine/VisualPinball.Unity/VisualPinball.Unity/Plugins/win-x64/VisualPinball.NativeInput.dll

Windows (MinGW)

cd VisualPinball.NativeInput
mkdir build
cd build
cmake .. -G "MinGW Makefiles" -DCMAKE_BUILD_TYPE=Release
cmake --build .

Linux

cd VisualPinball.NativeInput
mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
make

Requires: libx11-dev

macOS

cd VisualPinball.NativeInput
mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
make

Requires: AppKit and ApplicationServices frameworks (provided by macOS)

CI / NuGet

GitHub Actions builds win-x64, win-x86, linux-x64, osx-x64, and osx-arm64 binaries and packs them into a single NuGet package.

Publishing happens automatically for tags matching v*.

Usage from C#

using VisualPinball.Unity.Simulation;

// Initialize
NativeInputApi.VpeInputInit();

// Set bindings
var bindings = new[] {
    new NativeInputApi.InputBinding {
        Action = (int)NativeInputApi.InputAction.LeftFlipper,
        BindingType = (int)NativeInputApi.BindingType.Keyboard,
        KeyCode = (int)NativeInputApi.KeyCode.LShift
    }
};
NativeInputApi.VpeInputSetBindings(bindings, bindings.Length);

// Start polling
NativeInputApi.VpeInputStartPolling(OnInputEvent, IntPtr.Zero, 500);

// Callback
[MonoPInvokeCallback(typeof(NativeInputApi.InputEventCallback))]
static void OnInputEvent(ref NativeInputApi.InputEvent evt, IntPtr userData) {
    Console.WriteLine($"Input: {evt.Action} = {evt.Value} @ {evt.TimestampUsec}μs");
}

// Stop polling
NativeInputApi.VpeInputStopPolling();

// Shutdown
NativeInputApi.VpeInputShutdown();

Platform Status

Performance

• Latency: <0.1ms from physical input to event callback
• CPU Usage: 5-10% of one core (mostly sleeping)
• Overhead: ~10-20ns per P/Invoke call
• Precision: Monotonic microsecond timestamps across platforms

Future Enhancements

1. Gamepad support: XInput (Windows), SDL/libinput (Linux), GCController (macOS)
2. Analog inputs: Plunger, steering, analog triggers
3. Force feedback: Haptics for nudge, tilt, button feedback
4. Hot-plugging: Detect device connect/disconnect
5. Configuration: JSON-based key mapping files
6. Profiles: Per-table input profiles

License

GPLv3+ (same as VPE)